The present invention relates to a filter for gases, particularly air. A filter system of this type, which can be used to eliminate pollutants and odorous substances from airflows, is disclosed in examined European patent application no. EP 100,907 (=DE 32 28 156). The disclosed filters are described as useful for building interiors as well as for the passenger compartments of motor vehicles.
The occupants of vehicles, particularly motor vehicles, are exposed to two influences: pollutants, such as CO, NOx and, to a lesser degree, SO2, which cannot be smelled or are difficult to smell unless they are present in high concentrations, and odorous substances, which largely consist of incompletely burned fuel, particularly diesel fuel. For the typical motor vehicle user, odorous substances are a considerable nuisance.
Pollutants such as CO and NOx are difficult to eliminate according to the current state of the art, and their elimination requires bulky filter systems for which there is normally no space available.
Odors cannot be measured; they are a sensation. They are unusual in that they can be sensed even at very small concentrations and if they are disagreeable they are perceived as annoying. By means of tests conducted with a stationary diesel engine it was shown that despite diluting the exhaust 100,000 times with fresh air, a perceptible disagreeable odor persisted. It is therefore not surprising that it takes special filters to keep odors from road traffic from entering the interior of vehicles.
In the prior art, the known filter systems are maintained or serviced by removing dirty particle filters from the filter system and disposing of them. They have to be replaced on the one hand because dust particles accumulate and cake causing increased flow resistance. On the other hand the dust layer contains not only mineral dusts but also biologically active materials (bacteria, fungal spores), which germinate or multiply under suitable temperature and humidity conditions. Microbiological growth can lead to an explosive increase and colonization of the filter media, growth throughout the filter media, odor development, and protein-containing contaminants.
The necessity of servicing filter systems by replacing the particle filters increasingly conflicts with the requirements for a long service life of the filter systems. This applies to the replacement intervals for intake air filtration both in buildings and in vehicles. While the continued development of filter materials has made it possible that particle filtering and gas filtering properties satisfy these requirements over a prolonged period of time, the longterm use of such filter systems is prohibited because of the risk of microbiological contamination.
Accordingly, it is an object of the invention to provide an improved air filter with biocidal properties.
Another object of the invention is to provide an air filter material which is resistant to microbiological colonization by bacteria, yeasts and molds.
It is also an object of the invention to provide an air filter material which avoids or overcomes the disadvantages described above.
These and other objects have been achieved in accordance with the present invention by providing a filter for gases comprising an air permeable support, an adsorption filter layer and at least one biocidal additive attached to at least one of the support and the adsorption filter layer.
A significant advantage of the invention is that biocidal substances with long-term action can be added to the adsorptive material. Because the biocidal agent is slowly and continuously released, any material in the particle layer capable of germinating is permanently killed and can therefore not trigger any microbiological growth.
In accordance with a further embodiment of the invention, the adsorptive filter layer is comprised of activated carbon or polymer adsorbents, silica gel or zeolite. The adsorptive filter layer, of course, can also be created from a combination of these or other suitable adsorbents. A preferred mixing ratio for the biocidal additive is a proportion of 3% to 30%, preferably 10% of the mass per unit area of the adsorption filter layer. This ensures on the one hand that a high adsorptive volume is available and on the other hand that the biocidal action is sufficient to effectively kill even under unfavorable environmental conditions the spores or living fungi that are capable of germinating. A suitable biocidal additive is iodine or triiodide, which is incorporated in a polymer or an activated carbon adsorbent.
In a further embodiment of the invention, the filter is constructed as a combination filter, i.e., it consists of a supporting layer, a filtration layer, and a filtering cover layer. Several filtration layers can of course also be arranged in succession to achieve a higher degree of filtration.
According to a further embodiment of the invention, the filter material can be a three-dimensional filter structure comprised of an open-cell supporting structure with adsorbents and biocidal agents embedded therein or adhered thereto.
These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or the drawings, and the individual features each may be implemented in embodiments of the invention either alone or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.